The present invention is directed to a drill chuck for holding tools or bits in hand-held devices such as percussion drills, hammer drills and the like with the drill chuck including a chuck member provided with a thread on its exterior surface, a guide sleeve enclosing a portion of the chuck member and at least two clamping jaws supported in the chuck member so that they can be radially displaced. An adjustment adapter axially displaces the guide sleeve and, in turn, the guide sleeve radially positions the clamping jaws. The adjustment adapter and the guide sleeve can be displaced axially relative to the chuck member.
In drill chucks which simultaneously transmit rotational and percussion movement to a tool or tool bit, there are two different types of clamping action.
In a positive locking action, the insertion end of the tool has recesses or protrusions with which the clamping jaws engage in a positive locking manner. In such a chuck, radial play present between the clamping jaws and the end of the tool affords a limited axial movement within the drill chuck.
If a frictional locking action is provided, the insertion end of the tool does not have any recesses or protrusions and has a smooth surface. The clamping jaws are pressed radially against the insertion end during the clamping action by means of the drill chuck. The transmission of torque and the axial retention of the tool takes place only by way of the frictional lock which, in turn, depends on the applied clamping force. To prevent a loosening of the tool because of vibration developed in operation, such a clamping force must be considerable.
In previously known clamping chucks for hammer drills, percussion drills and the like, auxiliary tools are required for obtaining a frictional lock to exert the required clamping force. Such auxiliary tools are, for instance, gear rim wrenches which can be brought into engagement with a set of teeth arranged on the adjustment adapter and the adjustment or tightening action can be cumbersome and time consuming. Moreover, it is possible to leave the wrench engaged so that is represents a considerable possibility of injury when the hand-held device is operated. If the operator misplaces or loses the the wrench, a new wrench must be obtained to change the tool and delays may be caused in using the device. Quick clamping drill chucks using frictional locking and actuatable without auxiliary tools have not found any practical acceptance up to the present time in hammer drills, percussion drills and the like. Such lack of acceptance occurs because such chucks are very complicated and thus not economical. In addition, the clamping forces attained in the chuck depend to a great degree upon the torque developed during operation of the device, whereby the tool is not sufficiently tightly clamped or it is necessary to use a tool to open the chuck.